This investigation focuses on neuroblastoma-associated antigens that are on neural differentiation molecules, on embryonic or fetal molecules, or on peptides coded for by oncogenes. These molecules may contribute to the neoplastic phenotype and, because of their selective expression by tumor cells, may be useful targets for immunodiagnosis and immunotherapy. Recently developed methods for producing purified and defined immunogens are being used to make a new generation of monoclonal antibodies against gangliosides (DG2) and oncogene products (N-myc). These new antibodies and those produced previously are being used to investigate the relationship of antigen expression to the malignant phenotype. Immunodiagnostic studies aim to improve differential diagnosis, prognostication, monitoring, and identification of tumor cells in bone marrow. A panel of monoclonal antibodies has been defined that distinguishes neuroblastoma from other small round cell tumors. A very poor prognosis is indicated by elevated neuron-specific enolase and ferritin in serum and genomic amplification of N-myc. Using immunohistology, one neuroblastoma cell among 105 normal cells can be detected; this has been very useful for evaluating marrow prior to autologous transplantation. This investigation should contribute to a better understanding of neuroblastoma and to the development of new and improved diagnostic and therapeutic strategies. (AG)